HO: Count neighbor measurements and reduce window of neigh_meas_avg

Always start with a counter of 0 for a new measurement report. If the
neigh_meas_avg is caluclated over the given window, the window is
reduced, if there are less measurement reports received so far.

Change-Id: I1c74f27f9663a3083610c985a080fca331c19bd3
diff --git a/src/libbsc/handover_decision.c b/src/libbsc/handover_decision.c
index a2abb39..04ca144 100644
--- a/src/libbsc/handover_decision.c
+++ b/src/libbsc/handover_decision.c
@@ -99,6 +99,13 @@
 	unsigned int i, idx;
 	int avg = 0;
 
+	/* reduce window to the actual number of existing measurements */
+	if (window < nmp->rxlev_cnt)
+		window = nmp->rxlev_cnt;
+	/* this should never happen */
+	if (window == 0)
+		return 0;
+
 	idx = calc_initial_idx(ARRAY_SIZE(nmp->rxlev),
 				nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev),
 				window);
@@ -177,6 +184,7 @@
 		nmp->arfcn = mrc->arfcn;
 		nmp->bsic = mrc->bsic;
 
+		nmp->rxlev_cnt = 0;
 		idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev);
 		nmp->rxlev[idx] = mrc->rxlev;
 		nmp->rxlev_cnt++;